The disclosure generally relates to measuring the bandwidth of an optical multi-mode fiber (MMF) and, more particularly, relates to methods and configurations for testing an MMF by signal transmission and receipt on one end of the fiber.
Bandwidth is an important attribute of MMF product. Ultimately, bandwidth is used in the optical fiber industry to set the grade of the MMF product. The bandwidth is directly related to how the refractive index profile of the MMF exists in practice compared to the ideal, optimal profile for a given MMF configuration. The bandwidth exhibited by a given MMF is generally very sensitive to even a slight deviation from the ideal, optimal profile.
One method for measuring the bandwidth of an MMF is to apply a light signal at one end of the MMF, receive the transmitted light signal at the other end, and measure bandwidth through the known, differential mode delay (DMD) measurement technique. The DMD method records the time delay pulse using a controlled offset launch from a single mode fiber, and this offset is varied across the face of the fiber under test. Further, data processing is used to convert the time pulses versus offset position into a bandwidth result. The time for each DMD measurement is long, typically about 5-11 minutes.